E170: Calcium Carbonate

What is E170 (Calcium Carbonate)?

Calcium carbonate (E170) is one of the most abundant minerals on Earth, found naturally as chalk, limestone, marble, and calcite. It is the main component of shells of marine organisms, pearls, and eggshells. In food applications, it serves multiple roles: as a white food coloring, anti-caking agent, acidity regulator, and importantly as a source of dietary calcium in food fortification. It is chemically identical to the active ingredient in many antacid products.

Source and Production

Calcium carbonate for food use comes from two main sources:

Natural Extraction:

Limestone or chalk deposits are mined 2. The mineral is crushed, purified, and milled to fine particle sizes 3. Food-grade material meets stringent purity specifications

Synthetic Precipitation:

Calcium hydroxide solution is treated with carbon dioxide 2. Calcium carbonate precipitates as ultra-fine particles 3. Precipitated calcium carbonate (PCC) offers more consistent particle size

The resulting white powder is odorless and practically tasteless.

Common Uses in Food

E170 has multiple applications in food:

White confectionery coating and decorations
Bread and flour products (as a calcium supplement and improver)
Pastries and baked goods
Chewing gum (as a filler and calcium source)
Dietary supplements and fortified foods
Wine (as an acidity regulator)
Antacid products
Mineral waters
Some cheeses

Health and Safety

Safety Profile

Calcium carbonate has an outstanding safety profile:

Essential mineral: Calcium is a vital dietary nutrient; carbonate is a simple, easily metabolized anion
Long history of safe use: Used in food and medicine for centuries
Beneficial supplementation: In fortified foods, provides an important dietary calcium source
Antacid effect: Useful for managing heartburn and indigestion

Potential Concerns at High Intake

Hypercalcemia: Excessive calcium carbonate supplementation (far beyond food additive levels) can cause hypercalcemia (too much calcium in blood) — not a concern from typical dietary exposure
Milk-alkali syndrome: Very high chronic intake from supplements can cause alkalosis, hypercalcemia, and kidney damage — again, not relevant to food additive use
Constipation: Large amounts may contribute to constipation
Drug interactions: Can interfere with absorption of certain medications (tetracyclines, iron supplements, thyroid medications) if taken simultaneously

Regulatory Status

European Union: Fully approved as E170 without restriction
United States: GRAS (Generally Recognized As Safe); widely used in food fortification
ADI: Not specified — no numerical limit established due to high safety confidence

Identification on Labels

Calcium carbonate may appear as:

E170
Calcium carbonate
Chalk
Limestone (when used as a processing aid)
CaCO3

Conclusion

E170 (Calcium Carbonate) is one of the most benign food additives in use. As a naturally occurring mineral that serves as an important dietary calcium source, it not only poses negligible safety concerns at food additive levels but can actually be beneficial for bone health. It exemplifies how some food additives can be entirely natural substances that add genuine nutritional value. For consumers looking to make informed choices about food additives, calcium carbonate is among the least concerning entries in the E-number system.